1. Technical Field
This description pertains generally to a chemistry system for three-dimensional (3D) imaging, and more particularly to a bench-top radiochemistry system for 3D imaging.
2. Background Discussion
Positron Emission Tomography (PET) is a dynamic 3D imaging modality that can be used for microorganisms, cells, animals, plants, and humans to quantitatively measure biochemical processes in vivo. It uses “probes” (e.g. small molecules, peptides, proteins, nanoparticles, etc.) that are labeled with positron-emitting radioisotopes such as fluorine-18, carbon-11, nitrogen-13, oxygen-15, iodine-124, and copper-64, which interact on a molecular level with the biological system under study. Thus, PET can provide insight into various functional questions about biology, such as the distribution of metabolic activity (rate) in an organism, the spatial distribution of a target (e.g. cell surface marker or receptor); the movement of cells or microorganisms, the quantification of gene expression levels, the pharmacodynamics and pharmacokinetics of drug perturbation, and many other processes. Due to the high sensitivity of radiation detectors, PET is extremely sensitive compared to other imaging modalities, and can be accomplished with trace amounts of the probe, thereby not further perturbing the biological system under study. Additionally, due to the ability of energetic gamma rays (emitted after annihilation of positrons) to penetrate thick objects, PET can quantitatively image deep inside animal and plant tissues, enabling visualization of processes that cannot be easily seen with optical methods involving fluorescence or bioluminescence. Thus, PET provides a powerful way to safely study biology that can be translated across cells, plants, animals, and humans.
While PET would offer many advantages to the research community if a diversity of probes were routinely available, accessibility to the ˜3,000 known probes is very limited. In fact, the majority of PET studies (˜90%) employ only one probe, the glucose analog, 2-fluoro-2-deoxy-D-glucose (FDG). Due to their short half-life, as determined by the radioactive isotope they are tagged with (i.e. fluorine-18, ˜110 min), probes must be chemically synthesized immediately before use in a manner that provides safety and reliability to the user. Currently, PET probe production is expensive and requires a large capital investment in infrastructure (e.g. cyclotrons, cumbersome lead-shielded chemistry “hot cells”, purification systems, etc.) and specially trained personnel (for radiochemistry and cyclotron operation). Thus, the bulk of PET probes are produced in a centralized manner by commercial PET radiopharmacies established for clinical use of PET, with limited capacity and expertise, and high operating costs that restrict them from including production of new imaging probes. A number of universities have the same infrastructures as the commercial radiopharmacies. In these academic programs, production of probes is also complex, costly, and maintains a limited capacity to provide the diversity in molecular probes that matches the diversity of disciplines and biological problems to be studied.